This application is directed to the art of pipe joints, couplings, connectors and more particularly, to tee joint coupling constructed for plastic pipe or tubing. The invention is particularly applicable to connecting corrugated plastic tubing laterals with a larger diameter corrugated plastic tubing main and will be described with particular reference thereto. It will be appreciated, however, that the invention has broader applications and may be incorporated as an integral part of the tubing or may be sized and configured to accomodate connecting different tubings, different sizes of tubings, or tubing connections with different angular orientations such as a Y coupling.
Corrugated plastic tubing is widely used for many types of drainage systems and filtration systems. Corrugated tubing is typically molded of a high density polyethylene or polyvinylchloride and is supplied in continuous lengths. The tubing is generally cylindrical and has corrugated internal and external wall surfaces defined by adjacent circumferentially extending, longitudinally spaced peaks and valleys along the length of the tubing. Lengths of corrugated plastic tubing are interconnected at generally T-shaped and other intersections.
In a subterranean installation for drainage or septic purposes, it is common to have a corrugated plastic tubing main sized to carry a relatively large flow of fluid materials. Commonly corrugated plastic tubing laterals are sized to carry a lesser flow of fluid materials and are connected with the main by generally T-shaped intersections. Heretofore, there have been many different types and styles of tee joints or couplings. Tee couplings are commonly simple in construction to facilitate ease of assembly. Yet, the couplings should be strong in construction to resist forces exerted by the earth which is back filled in burying a subterranean installation. The amount of physical manipulations required to connect a lateral and the main with a tee coupling is reflected in the cost of installation of a subterranean tubing system. Prior couplings have included a conventional slip or external tee such as that shown in U.S. Pat. No. 3,551,007. To install such a tee, it is necessary to cut and remove a section of the theretofore continuous main and insert the slip tee in its place. If the lateral is of a lesser diameter than the main, a reducer is inserted between the tee and the lateral. Prior couplings also include the "saddle tee"such as that shown in U.S. Pat. No. 3,669,473. To install such a tee, a hole is cut in the side of the main, the earth excavated below the main adjacent the hole, and the tee expanded and snapped around the main, fitting like a tight saddle. A third tee coupling or connection has been made by cutting a hole in the side of the main and ramming a smooth wall tubing adapter, such as the adapter shown in U.S. Pat. No. 3,471,179, forcibly or loosely into the aperture.
Although these tee couplings and connectors have proved to be reasonably successful, there are some deficiencies which detract from their use. The slip and saddle tees are relatively large, require a relatively large amount of plastic to manufacture and are bulky to transport. Inserting a slip or saddle tee requires a relatively large amount of manipulation. The required manipulation includes not only drilling or cutting the main, but may require lifting the main and excavating under it or regrading to accomodate that part of the tee coupling which extends below the bottom surface of the main.
The other disadvantage of the prior art is that cutting a hole in the side of the main greatly reduces its strength. To compensate for the lost strength, slip and saddle tees are generally constructed with relatively thick walls. The smooth-walled tubing adapter provides substantially no reinforcement for the cut and weakened main. In addition to weakening the main, the use of a smooth-walled tubing adapter obstructs the flow of fluids through the main by protruding into it. It is clearly desirable to reduce the manipulative steps required to insert a tee coupling and to minimize a decrease in the strength of a tee coupling.
The present invention contemplates a new and improved tee coupling which provides simpler installation with greater strength than the prior art tee couplings. Further, this invention contemplates a tee connector which is simpler and more economical to manufacture.